How do you set the frame size of cv.CreateVideoWriter

Question

if I try:

writer = cv.CreateVideoWriter(file, -1,(int(800),int(600)), is_color=1)

-or-

writer = cv.CreateVideoWriter(file, -1,(800,600), is_color=1)

-or-

writer = cv.CreateVideoWriter(file, -1,(800.0,600.0), is_color=1)

I get the error:

TypeError: a float is required

with this I get progress:

writer = cv.CreateVideoWriter(file, -1, 25.0, (800,600), is_color=1)

error: Gstreamer Opencv backend doesn't support this codec acutally.

The input files are .png, the output is .avi

What happened to the comment with the float suggestion? – linuxrules94 Jul 28 '11 at 01:51 — linuxrules94, Jul 28 '11 at 01:51

Tugrul Ates · Accepted Answer · 2011-07-28T01:58:26.087

2

You need to pass a valid fourcc and fps:

fourcc = cv.CV_FOURCC('X','V','I','D')
fps = 25.0 # or 30.0 for a better quality stream
writer = cv.CreateVideoWriter(file, fourcc, 25.0, (800,600), is_color=1)

Alternatively, you can use named parameters in Python. It is less error-prone this way:

writer = cv.CreateVideoWriter(
    filename=file,
    fourcc=cv.CV_FOURCC('X','V','I','D'),
    fps=25.0,
    frame_size=(800,600),
    is_color=1)

A fourcc is an 32bit identifier of the codec of the video stream inside your target avi. Possible values for gstreamer according to cap_gstreamer.cpp are:

cv.CV_FOURCC('H','F','Y','U') # HuffYUV
cv.CV_FOURCC('D','R','A','C') # BBC Dirac
cv.CV_FOURCC('X','V','I','D') # MPEG-4 Part 2
cv.CV_FOURCC('X','2','6','4') # MPEG-4 Part 10 (aka. H.264 or AVC)
cv.CV_FOURCC('M','P','1','V') # MPEG-1 video

I believe all of the above can be put inside an avi container.

edited Jul 28 '11 at 01:58

answered Jul 28 '11 at 01:34

Tugrul Ates

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Some progress was made see above – linuxrules94 Jul 28 '11 at 01:45
What happened to the comment with the float suggestion? – linuxrules94 Jul 28 '11 at 01:50
@linuxrules94: I was wrong. You were passing your resolution pair where your fps must go. That's why OpenCv was complaining for not getting a float. I thought it also did expect floats for size values, which doesn't make much sense. – Tugrul Ates Jul 28 '11 at 02:05
@linuxrules94 - There you go :) Welcome to Stack Overflow! – Tugrul Ates Jul 28 '11 at 02:13
That's Ironic: I just sent that comment and when I did I got privilege to upvote. @junjanes – linuxrules94 Jul 28 '11 at 02:15
I still get errors with any of the above codecs: Gstreamer Opencv backend doesn't support this codec acutally. – linuxrules94 Aug 02 '11 at 20:34
@linuxrules94: Please add your OS and OpenCv version in the question. – Tugrul Ates Aug 03 '11 at 02:55
Linux opensuse 11.4, opencv 2.2.0 See here: http://stackoverflow.com/questions/6918995/opencv-error-on-python – linuxrules94 Aug 03 '11 at 16:14

How do you set the frame size of cv.CreateVideoWriter

1 Answers1